Nickel plating solution and method for forming nickel plating layer using the same

ABSTRACT

Disclosed herein are a nickel plating solution and a method for forming a nickel layer on an external electrode of a chip component by using the nickel plating solution, the nickel plating solution including: a nickel ion; a chloride ion; and a pH buffer, wherein the pH buffer is used by mixing an inorganic acid, and an organic acid and a salt thereof, so that the damage to a body of the chip component can be reduced by containing organic acid and a salt thereof in the nickel plating solution for forming the nickel plating layer on the external electrode of the chip component having a body formed of a material including ferrite or manganese oxide.

CROSS REFERENCE(S) TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. Section 119 ofKorean Patent Application Serial No. 10-2012-0100435, entitled “NickelPlating Solution and Method for Forming Nickel Plating Layer Using TheSame” filed on Sep. 11, 2012, which is hereby incorporated by referencein its entirety into this application.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a nickel plating solution and a methodfor forming a nickel plating layer using the same.

2. Description of the Related Art

In general, as an external electrode of a chip component amongelectronic components, a nickel or tin plating layer is formed on anunderlayer metal material through electroplating. The tin plating layeris used as a soldering layer at the time of mounting a printed circuitboard, and the nickel plating layer serves as a barrier layer betweenthe external electrode and a solder.

For the nickel plating layer, a nickel electroplating solution is usedand a sulfamate bath or a watt bath is mainly used. However, in the casewhere a conventional nickel plating solution is used, a body of theelectronic component may be damaged depending on the material of theelectronic component.

A general nickel plating solution for the chip component is composed ofthe following chemicals. In the case of the sulfamate bath, nickelsulfamate is used as a nickel metal source, and in the case of the wattbath, nickel sulfate is used as a nickel metal source.

Commonly, in order to help anodic dissolution, nickel chloride is usedas a chloride ion source, and boric acid is mainly used as a buffer anda pH adjuster. In addition, the plating solution is made up and used ata region of pH of 4.5 or lower.

However, in the case where the body is formed of materials containingferrite or manganese oxide, the formation of the plating layer of ageneral nickel electroplating solution may cause the body to be damaged.For example, since the body is worn, electric property may bedeteriorated; the plating solution may penetrate into a neighboringportion of the external electrode; or the external electrode may belifted or peeled due to the wearing. In addition, the decrease inadhesive strength between the external electrode and the body may causeproducts to be defective.

In the related art, in the case where the body is damaged by the platingsolution, a surface of the chip is coated to minimize the contact withthe plating solution, and then plating is performed thereon. However, inthe case where coating is performed, costs and time are required due tothe use of an additional process before plating, and in the case wherethe quality of the coating film is bad, the risk of damage to productsis high.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a nickel platingsolution capable of minimizing damage without an additional process whena body of a chip component is formed of a material containing ferrite ormanganese oxide.

Another object of the present invention is to provide a method forforming a nickel plating layer on an external electrode of the chipcomponent by using the nickel electroplating solution.

According to one exemplary embodiment of the present invention, there isprovided a nickel plating solution, including: a nickel ion; a chlorideion; and a pH buffer, wherein the pH buffer is used by mixing aninorganic acid, and an organic acid and a salt thereof.

The pH buffer may be contained in a concentration of 30˜100 g/L and theorganic acid and the salt thereof may be contained in a concentration of20˜50 g/L in the pH buffer.

The organic acid and the salt thereof may be at least one selected fromthe group consisting of succinic acid, gluconic acid, lactic acid, and asalt thereof.

The nickel ion may be contained in a concentration of 50˜100 g/L and thechloride ion may be contained in a concentration of 10˜50 g/L.

The nickel plating solution may have a pH value of 4.5˜6.0.

According to another exemplary embodiment of the present invention,there is provided a method for forming a nickel plating layer in whichthe nickel plating layer is formed on an external electrode of a chipcomponent, wherein the nickel plating layer is formed by using a nickelelectroplating solution containing a nickel ion, a chloride ion, and apH buffer where an inorganic acid, and an organic acid and a saltthereof are mixed.

Here, a body of the chip component may be formed of a semiconductorceramic material including ferrite; or Mn, Ni, Al or Co.

The chip component may be an inductor or a thermistor.

The forming of the nickel plating layer may be performed under a DCcurrent application condition.

Here, in the forming of the nickel plating layer, a plating temperatureof the plating solution may be 45˜55° C.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an image of a lateral surface of a control group (a chipcomponent before plating);

FIG. 2 is an image of a lateral surface of a chip component after anickel plating layer is formed on an external electrode by using aplating solution of Comparative Example 1;

FIG. 3 is an image of a lateral surface of a chip component after anickel plating layer is formed on an external electrode by using aplating solution of Example 1;

FIG. 4 is a scanning electron microscope (SEM) image confirmingcorrosion or non-corrosion of a body when a nickel plating layer isformed on an external electrode of a chip component by using a nickelplating solution prepared according to Comparative Example 1; and

FIG. 5 is a scanning electron microscope (SEM) image confirmingcorrosion or non-corrosion of a body when a nickel plating layer isformed on an external electrode of a chip component including a materialcontaining manganese oxide in the body by using a nickel platingsolution prepared according to Example 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described in detail. Termsused in the present specification are for explaining the embodimentsrather than limiting the present invention. Unless explicitly describedto the contrary, a singular form includes a plural form in the presentspecification. Also, used herein, the word “comprise” and/or“comprising” will be understood to imply the inclusion of statedconstituents, steps, operations and/or elements but not the exclusion ofany other constituents, steps, operations and/or elements.

The present invention is directed to a neutral type nickel platingsolution for electroplating for forming a nickel plating layer formed onan external electrode of a chip component.

The nickel electroplating solution according to the present inventionincludes a nickel ion, a chloride ion, and a pH buffer, and the pHbuffer is characterized by mixing an inorganic acid, and an organic acidand a salt thereof.

In the present invention, the pH buffer is used by mixing an inorganicacid, and an organic acid and a salt thereof. For this reason, theproblem of the related art that the body is damaged due to the use ofonly an inorganic acid can be solved.

The reason why the body is corroded by the nickel electroplatingsolution of a general sulfamate bath or watt bath is a low pH value ofthe plating solution. In the case where the pH of the nickelelectroplating solution is raised to be 4.5 or higher, the body maybecome less corroded. However, with respect to a general nickelelectroplating solution, when the value of pH is raised by using a pHadjuster, for example, caustic soda, ammonia, or the like, the platingsolution cannot be used due to precipitation of hydroxides.

In order to prevent this phenomenon, it is necessary to use a pH buffer.The present invention solves this problem by using an organic acid and asalt thereof as well as the existing inorganic acid, as a pH buffer. Inparticular, in the case of using the organic acid and the salt thereof,the nickel ion is made into a complex salt so that the nickel ion isstably present in the plating solution, thereby preventing formation ofhydroxide precipitation.

Preferably, the pH buffer is contained in a concentration of 30˜100 g/Land the organic acid and the salt thereof are contained in aconcentration of 20˜50 g/L within the plating solution.

If the concentration of the pH buffer is below 30 g/L, the pH variationof the plating solution before and after plating may be increased,unfavorably. If above 100 g/L, chemicals may not be easily dissolved inthe plating solution, unfavorably.

In addition, if the concentration of the organic acid and the saltthereof in the pH buffer is below 20 g/L, the hydroxides may be easilygenerated at the time of an increase in pH value of the platingsolution. If above 50 g/L, there may be problems with dissolution ofchemicals and the plating efficiency may be reduced, unfavorably.

Examples of the organic acid and the salt thereof may include succinicacid, gluconic acid, lactic acid, sodium succinate, sodium gluconate,and the like, but are not limited thereto.

In addition, the pH buffer of the present invention includes an existinginorganic acid such as boric acid, and the inorganic acid may becontained in a concentration of 10˜50 g/L.

Preferably, the nickel ion is contained in the nickel electroplatingsolution of the present invention in a concentration of 50˜100 g/L.Examples of a nickel ion source may include nickel sulfamate, nickelsulfate, and the like, but are not limited thereto.

In addition, the chloride ion is preferably contained in the nickelelectroplating solution of the present invention in a concentration of10˜50 g/L. A chloride ion source may be nickel chloride, but is notlimited thereto.

In addition, the pH of the nickel electroplating according to thepresent invention is preferably maintained at a pH range of 4.5˜6.0. Ifthe pH of the plating solution is below 4.5, the body may be corroded,unfavorably. If above 6.0, the stability of the plating solution may bedeteriorated and thus it is difficult to use the plating solution for along time, unfavorably.

The plating temperature of the nickel electroplating of the presentinvention is preferably 45˜55° C., and as necessary, the platingsolution may be stirred.

In addition, the present invention is also characterized in a method offorming a nickel plating layer on an external electrode of the chipcomponent. Here, the nickel plating layer may be formed by using anickel electroplating solution containing a pH buffer where a nickelion, a chloride ion, inorganic acid, and organic acid and a salt thereofare mixed.

The nickel electroplating solution has been described in detail asabove.

The body of the chip component is preferably formed of a semiconductorceramic material including ferrite; or Mn, Ni, Al or Co. Arepresentative example of the ferrite is NiZnCu ferrite, but is notlimited thereto.

In view of forming the nickel plating layer on the external electrode ofthe chip component by using the nickel electroplating of the presentinvention, an inductor or a thermistor may be preferably used as thechip component.

In addition, when the nickel plating layer is formed on the externalelectrode of the chip component by using the nickel electroplatingsolution, electroplating is preferably performed under the DC currentapplication condition. The cathode current density is preferably in therange of 2˜10 A/dm².

Hereinafter, examples of the present invention will be described indetail. The following examples are only for illustrating the presentinvention, and the scope of the present invention should not beconstrued as being limited by these examples. Further, specificcompounds are used in the following examples, but it is obvious to thoseskilled in the art that equivalents thereof can exhibit the same orsimilar degrees of effects.

COMPARATIVE EXAMPLE 1

A plating solution containing a nickel ion of 80 g/L, nickel chloride of15 g/L, and boric acid of 15 g/L was prepared, and the pH of the platingsolution was adjusted by using sulfuric acid and nickel hydroxide.Nickel and tin electroplating was performed on an external electrode ofa chip component having a body containing manganese oxide, at atemperature of 50° C. by using the plating solution.

EXAMPLE 1

A nickel plating solution containing a nickel ion of 80 g/L, nickelchloride of 15 g/L, boric acid of 15 g/L, and succinate acid of 40 g/Lwas prepared, and the pH of the nickel plating solution was adjusted tobe 5.5 by using sulfuric acid and nickel hydroxide

Nickel and tin electroplating was performed on an external electrode ofa chip component, having a body (semiconductor ceramic including Mn, Ni,Al and Co) containing manganese oxide, at a temperature of 50° C. of thenickel plating solution, by using the nickel plating solution.

EXAMPLE 2

Plating was performed on a chip component in the same manner as Example1, except that sodium gluconate instead of succinate acid was used asthe organic acid of the nickel electroplating solution of Example 1.

CONTROL GROUP

With respect to a chip component having a body containing manganeseoxide before a plating layer is formed on an external electrode, as acontrol group, comparison of corrosion or non-corrosion of the body dueto formation of a nickel plating layer was conducted between the platingsolutions of Comparative Example and Examples.

EXPERIMENTAL EXAMPLE 1 Confirmation on Corrosion of Body

When each of the nickel plating solutions prepared according to Example1 and Comparative Example 1 was used to form a nickel plating layer onan external electrode of a chip component having a body containingmanganese oxide, corrosion or non-corrosion of the body was confirmed byobserving a cross section thereof through an optical microscope. Theresults were shown in FIGS. 1 to 3.

FIG. 1 is an image of a lateral surface of a chip component before anickel electrode layer is formed on an external electrode 20. Referringto FIG. 1, in the case of Comparative Example 1 where a nickel platinglayer was formed on an external electrode 20 by using a nickel platingsolution of the related art, a body 10 was corroded as shown in FIG. 2,so that it was observed that the thickness of the body (T2) wassignificantly decreased as compared with the thickness of the bodybefore plating (T1).

However, in the case of Example 1 where a nickel plating layer wasformed on an external electrode 200 by using a nickel plating solutioncontaining organic acid, the body 100 was not corroded as shown in FIG.3, so that it was confirmed that the thickness of the body (T3) ismostly similar to the thickness of the body before plating (T1).

Even in the case where the nickel plating layer was formed on theexternal electrode by using the nickel plating solution of Example 2,containing a different kind of organic acid, the body was not corrodedlike in Example 1.

EXPERIMENTAL EXAMPLE 2 Confirmation on Corrosion or Non-corrosionStructure of Body

When each of the nickel plating solutions prepared according toComparative Example 1 and Example 1 was used to form a nickel platinglayer on an external electrode of a chip component having a bodycontaining manganese oxide, corrosion or non-corrosion of the body wasconfirmed by using a scanning electron microscope. The results wereshown in FIGS. 4 to 5.

As can be seen from FIG. 4 showing a structure of the body according toComparative Example 1, excessive corrosion of the body occurred.However, as can be seen from FIG. 5 showing a structure of the bodyaccording to Example 1 of the present invention, corrosion of the bodydid not occur.

These results resulted from the fact that the organic acid and the saltthereof contained in the nickel plating solution of the presentinvention form a complex salt together with the nickel ion so that thenickel ion can be stably present in the plating solution even at thetime of increasing pH of 4.5 or higher, and thus effectively preventformation of hydroxide precipitation.

As set forth above, according to the present invention, the nickelelectroplating solution for forming a nickel plating layer on theexternal electrode of the chip component having a body formed of amaterial including ferrite or manganese oxide contains organic acid anda salt thereof, so that damage to the body can be reduced.

While the present invention has been shown and described in connectionwith the embodiments, it will be apparent to those skilled in the artthat modifications and variations can be made without departing from thespirit and scope of the invention as defined by the appended claims.

What is claimed is:
 1. A nickel plating solution, comprising: a nickelion; a chloride ion; and a pH buffer, wherein the pH buffer is used bymixing an inorganic acid, and an organic acid and a salt thereof.
 2. Thenickel plating solution according to claim 1, wherein the pH buffer iscontained in a concentration of 30˜100 g/L and the organic acid and thesalt thereof are contained in a concentration of 20˜50 g/L in the pHbuffer.
 3. The nickel plating solution according to claim 1, wherein theorganic acid and the salt thereof are at least one selected from thegroup consisting of succinic acid, gluconic acid, lactic acid, and asalt thereof.
 4. The nickel plating solution according to claim 1,wherein the nickel ion is contained in a concentration of 50˜100 g/L andthe chloride ion is contained in a concentration of 10˜50 g/L.
 5. Thenickel plating solution according to claim 1, wherein it has a pH valueof 4.5˜6.0.
 6. A method for forming a nickel plating layer in which thenickel plating layer is formed on an external electrode of a chipcomponent, wherein the nickel plating layer is formed by using a nickelelectroplating solution containing a nickel ion, a chloride ion, and apH buffer where an inorganic acid, and an organic acid and a saltthereof are mixed.
 7. The method according to claim 6, wherein a body ofthe chip component is formed of a semiconductor ceramic materialincluding ferrite; or Mn, Ni, Al or Co.
 8. The method according to claim6, wherein the chip component is an inductor or a thermistor.
 9. Themethod according to claim 6, wherein the forming of the nickel platinglayer is performed under a DC current application condition.
 10. Themethod according to claim 6, wherein in the forming of the nickelplating layer, a plating temperature of the plating solution is 45˜55°C.